title: Characterizing the S-layer structure and anti-S-layer antibody recognition on intact Tannerella forsythia cells by scanning probe microscopy and small angle X-ray scattering.
abstract: Tannerella forsythia is among the most potent triggers of periodontal diseases, and approaches to understand underlying mechanisms are currently intensively pursued. A ~22-nm-thick, 2D crystalline surface (S-) layer that completely covers Tannerella forsythia cells is crucially involved in the bacterium-host cross-talk. The S-layer is composed of two intercalating glycoproteins (TfsA-GP, TfsB-GP) that are aligned into a periodic lattice. To characterize this unique S-layer structure at the nanometer scale directly on intact T. forsythia cells, three complementary methods, i.e., small-angle X-ray scattering (SAXS), atomic force microscopy (AFM), and single-molecular force spectroscopy (SMFS), were applied. SAXS served as a difference method using signals from wild-type and S-layer-deficient cells for data evaluation, revealing two possible models for the assembly of the glycoproteins. Direct high-resolution imaging of the outer surface of T. forsythia wild-type cells by AFM revealed a p4 structure with a lattice constant of ~9.0 nm. In contrast, on mutant cells, no periodic lattice could be visualized. Additionally, SMFS was used to probe specific interaction forces between an anti-TfsA antibody coupled to the AFM tip and the S-layer as present on T. forsythia wild-type and mutant cells, displaying TfsA-GP alone. Unbinding forces between the antibody and wild-type cells were greater than with mutant cells. This indicated that the TfsA-GP is not so strongly attached to the mutant cell surface when the co-assembling TfsB-GP is missing. Altogether, the data gained from SAXS, AFM, and SMFS confirm the current model of the S-layer architecture with two intercalating S-layer glycoproteins and TfsA-GP being mainly outwardly oriented.
authors.affiliation: Institute for Biophysics, Johannes Kepler University Linz, Gruberstrasse 40, A-4020, Linz, Austria.
authors.forename: Yoo Jin
authors.initials: YJ
authors.lastname: Oh
authors.forename: Gerhard
authors.initials: G
authors.lastname: Sekot
authors.forename: Memed
authors.initials: M
authors.lastname: Duman
authors.forename: Lilia
authors.initials: L
authors.lastname: Chtcheglova
authors.forename: Paul
authors.initials: P
authors.lastname: Messner
authors.forename: Herwig
authors.initials: H
authors.lastname: Peterlik
authors.forename: Christina
authors.initials: C
authors.lastname: Schäffer
authors.forename: Peter
authors.initials: P
authors.lastname: Hinterdorfer
mesh_terms: D000907:Antibodies, Bacterial / Q000276:immunology*; D001426:Bacterial Proteins / Q000276:immunology; D001438:Bacteroidaceae / Q000166:cytology* / Q000276:immunology*; D006023:Glycoproteins / Q000276:immunology; D055767:Immobilized Proteins / Q000737:chemistry; D007700:Kinetics; D008562:Membrane Glycoproteins / Q000276:immunology*; D018625:Microscopy, Atomic Force; D020527:Microscopy, Scanning Probe; D053838:Scattering, Small Angle; D013057:Spectrum Analysis; D013816:Thermodynamics; D014961:X-Ray Diffraction
chemical_list: D000907:Antibodies, Bacterial; D001426:Bacterial Proteins; D006023:Glycoproteins; D055767:Immobilized Proteins; D008562:Membrane Glycoproteins; C055764:S-layer proteins
keywords: S-layer structure; Scanning probe microscopy; Tannerella forsythia; antibody recognition; force spectroscopy; small-angle X-ray scattering